Embodiments of the present invention relate to impact tools for use in drilling operations, and more particularly, to fluid-actuated directional drilling equipment with an integrally formed bent sub and sonde housing.
Fluid-actuated directional percussive impact tools, such as drills, are commonly used for directional boring, which allows for the underground installation of pipes, cables, or the like without digging a trench. Drills for such operations typically include a back head for connection to a pressurized fluid source and a tool casing that houses a drill bit. A sonde housing that includes a sonde therein is typically arranged between the back head and the casing. The sonde can be used to transmit data, such as angle, rotation, or direction of the drill, temperature, or the like back to the driller above ground. Typically a bent sub (a small, angled piece of the drill string), is used to connect the sonde housing to the tool casing.
The angle of the bent sub allows the driller to steer the tool casing around obstacles that may be in the way of the planned route and/or to steer up or down to hit a set exit point of the drill. The bent sub is typically threaded on both ends, with one end being threaded onto the sonde housing and the other end being threaded onto the tool casing. However, the threaded connection can come loose while partially turning the tool casing during the steering process. The conventional method used in the industry to prevent loosening of the threaded connection is to weld or epoxy the joint together.
Although welding of the joint may aid in preventing disconnections for the short term, it does not provide a lasting solution. Welding changes the temper of the metal parts of the drill, making them brittle and more susceptible to cracks, which leak pressurized air needed to run the hammer and drill bit in the tool casing. As the hammer slows down due to the air loss, the driller puts more push pressure on the hammer. Eventually the added force causes complete failure at the welded joint. Similar to the weld, epoxy also eventually loosens and allows air leakage. Once loose, old epoxy needs to be removed and reapplied. Removal requires heat from a torch to soften the old epoxy. The heat will also make the metal of the drill brittle and the same type of cracking and failure experienced with welds can occur.
It is therefore desirable to provide a drill with a sonde housing and bent sub that will not loosen during turning of the drill but does not utilize methods that adversely affect the material of the drill to the point of cracking and air leakage.